(1) Field of the Invention
The present invention relates to communication systems, and more particularly, to a communication system that performs a communication control.
(2) Description of the Related Art
Amazing popularization of the Internet has stimulated very active information communications such as audio and image. Recently, business users such as companies have positively considered the introduction of IP-VPN (Internet Protocol Virtual Private Network) in order to reduce the communication cost and realize electronic commerce.
The concept of QoS (Quality of Service) is needed to realize the Internet such as a leased line in which the available band is ensured. However, the current condition of the Internet does not guarantee QoS in the network layer (that is, the current condition is the best effort).
Thus, two QoS guaranteed techniques have been proposed, one of which is Intserv (RFC2205), and the other is Diffserv (RFC2475). These techniques have been considered toward standardization in IETF (Internet Engineering Task Force). The IETF is an organization for standardizing Internet related techniques and is making up document groups such as various protocols (RFC: Request For Comments).
Intserv (Integrated Service) performs scheduling for each flow using a network router. The flow is a flow of packets having the same source address, destination address, source port number and destination port number. The scheduling is a process for determining the order of packets in packet processing.
Intserv is a way close to the connection type network, but requires the router to handle complex processing such as state management and scheduling on the flow basis. Therefore, as the network scale becomes larger, the load of the router increases. Thus, Intserv has a problem in scalability.
On the other hand, Diffserv (Differentiated service) does not perform the above-mentioned flow-basis control, but is aggregate flow-basis processing in which DSCP (Diffserv Code Point) in the packet header is designated, and the packets having the same DSCP are handled as the same QoS. It has been desired that Diffserv is practiced as a way with high scalability with respect to large-scale networks.
Recent communication networks have complexity and extremely large scales in order to provide various services. For example, a composite network layer structure has been employed in which an IP network is configured on an ATM network.
Also, techniques such as XDSL (x Digital Subscriber Line) or ATM-PON (Asynchronous Transfer Mode Passive Optical Network) have been practiced in the access section (from the user to the carrier station. In the access section, the band is guaranteed using QoS of the ATM.
Although QoS should be guaranteed in the end-to-end section, the conventional art guarantees the band only in part of the access section on the ATM basis in the above-mentioned communication network. Thus, the original effects of QOS are not brought about, and the communication quality and the reliability are thus degraded.
It is therefore necessary to efficiently perform the interface control of QoS between the Diffserv compliant node and the ATM node in communications via the network including IP and ATM and to guarantee end-to-end QoS and the network.